Air-Broadened Linewidth Measurements in the ν2 Vibrational Band of the Hydroperoxyl Radical

Abstract We have measured the air-broadening coefficient for one of the strongest infrared absorption lines of the hydroperoxyl radical-the 9 19 ← 8 18 F 1 , F 2 doublet of the ν 2 band at 1411.18 cm −1 . We obtain a value of b = 0.107 ± 0.009 cm −1 atm −1 (half-width at half-maximum) for the Lorentz broadening caused by air at 296 K. This measurement was made using a high-resolution tunable diode laser. The HO 2 was made at atmospheric pressure from the H + O 2 association reaction. The HO 2 was sampled by a fast-flow reduced-pressure multipass absorption cell using an astigmatic off-axis resonator. The optical path length was 100 m with 182 passes. The results of this measurement are essential for the design and implementation of several atmospheric hydroperoxyl monitoring schemes.